As the battle for control of Congress enters its final weekend, election experts warn that the number of voters forced to cast provisional ballots Tuesday because of eligibility questions could delay some results in tight races for days or weeks.

Eight weeks before elections that will decide control of Congress, a rush by state and local governments to prepare new voting machines and train poll workers is raising the possibility of trouble reminiscent of the 2000 presidential election standoff.

The glitches in this year's primaries come as nearly one in three counties wrestle with new equipment upgrades mandated by the Help America Vote Act of 2002. The law was intended to fix the type of problems that plagued the 2000 presidential election.